Method for impregnating acrylonitrile polymer fibers to improve dyeability



Jan. 3, 1967 H. P. BRIAR ET AL 3,296,341

METHOD FOR IMPREGNATING ACRYLONITRILE POLYMER FIBERS TO IMPROVEDYEABILITY Filed July 15, 1963 1 1/67 5 m acr /0n/'//'/'/e 0/ mar la ino 56/ f'i/amnf W056 ff/am en 74%? e from res/au a/ so/ven Pa 2" 5/ e/c/z14/0/7723 f5 af so //0"c Re/a! ff/amen/s in dye asslls/an/ So/u/fon 0/90//0c INVENTORS. Herman 1 Brian BY Ruper/ 5 Hur/ey Mzm United StatesPatent 9 This invention contributes to the synthetic fiber art and hasparticular reference to enhancing the dyeability of synthetic fibers.Particularly, it relates to a method for impregnating wet-spunacrylonitrile polymer fibers while they are in a freshly formed gelcondition with a dye assistant to improve the dyeability of the fiber.

Synthetic fibers, including acrylonitrile polymer fibers,

have always been difiicultly dyeable in contrast to the commonlyavailable natural fibers, e.g., cotton and Wool. Several methods havebeen pursued in attempting to solve the inherent and attendantdifiiculties encountered with acrylonitrile polymer or acrylic fiberdyeability. Among these have been the development of dyestuffs orparticular dyeing procedures specifically designed for or especiallysuited to the polymer structure. Other schemes include building into thepolymer structure sites which are receptive to dyestuffs such as might'be accomplished by certain additaments that are copolymerized withacrylonitrile to fiber forming polymers, or by incorporating in theacrylonitrile polymer a dye receptive polymer by blending the twopolymers prior to extruding or spinning the polymer composition to formthe filament or fiber.

Although the foregoing means have frequently led to better dyed ordyeable fibers, there are certain attendant disadvantages associatedwith each. For instance, when dyestuffs are especially synthesized forpolyacrylonitrile, the dyestuffs are apt to be quite expensive, andadditionally, the range of shades and colors is usually limited orlacking in desirable fastness properties. Or, particularly when dyereceptive sites are built into the polymer chain throughcopolymerization of another monomer with acrylonitrile there is mostalways observed a sacrificial loss in some of the inherent properties sodesirable in the polyacrylonitrile backgone, such as tensile strength.Blending a dye-receptive polymer with the polyacrylonitrile prior tospinning presents mixing problems to attain uniformity and may requirerather large energy requirements. Another method sometimes employed, isto add color, generally in the form of a pigment, into the spinningsolution, frequently called spinning dope. This method, however, has theinherent disadvantage of contaminating the polymer handling andconveying systems with colored bodies which must be dealt with whenplain white fibers are subsequently to be manufactured in the sameequipment.

One means that has been rather successfully employed to overcome some ofthe above-indicated disadvantages when acrylonitrile polymers arewet-spun is to impregnate the freshly spun fiber while it is in a gelcondition with a dye receptive additive, such as a polymer (which willhereinafter be referred to as dye assistant). One difficulty that hasbeen observed with this method is that frequently the running length offibers are not uniformly impregnated along the length of the fibers, andadditionally, the dye assistant does not penetrate the gel structure butremains only on the periphery of the fiber surface or at best onlyslightly penetrates the gel'structure. This results in ring dyeing ofthe fiber, i.e., dyeing on the surface. This in itself is not always hadsince often times good coloration is achieved when the fiber is dyed.The deficiencies of the method ordinarily make themselves known when thedyed fibers are subjected to abraid- 'ice ing forces, such as thoseinduced during the wearing by an individual of a garment made of thefibers, or those induced during some of the textile processingtreatments. The result is that the fibers tend to objectionably whitenor become lighter in shade, particularly at wear points. This may be aresult of the color lying on the surface of the fiber being worn off andexposing the undyed portions of the fiber underneath, or, sometimes, itmay be a result of the dye assistant build-up on the fiber surfaceweakening, as for instance by tending to plasticize the acrylonitrilepolymer, such that actual fibrils may peel back from the surface. Thishas the dual effect of exposing the undyed portions of'the fiber and ofthe fibrils dispersing the incident light so that a frosted appearanceis presented. A secondary drawback of any surface build-up of the dyeassistant on the gel fiber surface is that oftentimes the adjacentfibers will fuse during the drying of the fibers causing objectionablelarge fibers or sticks to form.

Accordingly, it is the chief aim and primary object of the presentinvention to provide an improved and highly efiicient method forincorporating a dye assistant in acrylonitrile polymer gel'fiberswhereby the dye assistant is uniformly and deeply and frequentlythoroughly penetrated throughout the cross-section of the fiber anduniformly distributed along the fiber length so that the fibers in anirreversibly dried form can be dyed to excellent shades of colorationhaving good resistance to whitening and fibrillation.

In accordance with the present invention, a method is provided forincorporating a dye assistantin acrylonitrile polymer gel or aquagelfilaments comprising spinning a solution of a polymer of anethylenically unsaturated monomeric material containing at least aboutweight percent polymerized acrylonitrile into an aqueous coagulatingbath to form acrylonitrile polymer filaments; washing the filamentsessentially free of any residual acrylonitrile polymer solvent,partially stretching the washed filaments in an aqueous medium at 110C., immersing the washed and partially stretched filaments in a liquidbath at between about 90-l 10 C. containing dye assistant agent capableof enhancing the dyeability of the filaments and relaxing the filamentstherein, stretching the impregnated filaments at between about 90-100C., and subsequently, irreversibly drying the impregnated and stretchedfilaments to a textile fiber.

The sequence of steps of the invention is schematically illustrated inthe sole figure of the drawing.

The fibers prepared in accordance with the present invention possessexcellent physical properties in addition to being made through dyeableto excellent deep shades of coloration throughout the cross section aswell as along the length of the fibers. They ex-hi-bit outstandingresistance to fading from exposure to washing and light as well as towhitening and fibrillation. The present inventive method provides ahighly expedient and efficient means for continuously, rapidly,uniformly and reproduceably preparing acrylonitrile fibers that can bedyed with a wide variety of dyestuffs.

The residence time of the gel fiber in the impregnating bath is extremlyshort, i.e., usually on the order of to second, although much longertimes can be employed if desired. Despite-this unusually short cycle,the fiber is uniformly impregnated frequently throughout thecrosssection of thefiber as well as lineally. Not only is each filament"uniformly impregnated throughout, but the complete tow which mayconsist of thousands of filaments and be of 100,000 or so total denieris uniformly impregnated throughout. That is, fiber-to fiber variation'is usually minimal.

The reasons for the marked improvement in penetration of the dyeassistant into the gel filament structure with practice of the presentinvention is not fully understood. It is evidently related to themorphological phenomena that take place during the transformation of thepolymer in solution to the stretched gelled filament. Thus, thecombination of pre-and post-impregnation stretch combined with theintermediate relax in the dye assistant solution allows for and enhancesuptake and penetration of the assistant even when the dye assistantitself is a high molecular weight polymer. There are apparently severalfactors that may influence the uptake and penetration of the dyeassistant. It has been noted that stretching the gel filament to thepoint where it has normally acceptable physical properties, i.e.,stretched to times, that a rather dense structure including outer skin,is presented which tends to inhibit penetration. Likewise, if the gelfilament is not stretched at all the structure is likely to 'be in askin-core state with a semi-soft core, but tight skin again resistingpenetration. If impregnation is carried on during stretching otherunknown factors tend to prohibit penetration. The present inventiontakes advaa-ntage of the finding that the particular sequence of stepsemployed provides a gel structure excellently adapted for the purpose ofaccepting a dye assistant throughout the structure.

Another feature that points up the novelty of the invention is that,strange as it may seem, if the dye assistant is present in the firststretch bath, i.e., the pre-impregnation stretch bath, in addition tobeing in the relaxing impregnation bath, the penetration of the dyeassistant is apparently interfered with so that inferior results areobtained.

The pre-impregnation stretch is carried out in aqueous medium, which may'be' steam, but preferably water, at about 90-1 10 C. Highertemperatures can be employed but ordinarily do not materially enhancethe results of the invention and may introduce deleterious effects.Penetration of the dye assistant tends to decrease quite readily whentemperatures of much less than 90 C., e.g., 70 C., are maintained in thepre-impregnation stretch. Depending somewhat on the composition of theacrylonitrile polymer and spinning conditions, e.g., solvent, coagulantand temperature, the stretch imparted to the gel filament in thepre-impregnation stretch may be from about 2 to about 12 times,beneficially a stretch between about 4 and 8 times, i.e., a stretchratio of 4:1 to 8:1, is utilized. Any suitable means may be employed toeffect the stretch which is most conveniently accomplished by stretchingthe filaments between two sets of pinch rolls with the down-stream setof rolls being driven at a faster rate than the up-s'treamgolls.

After the pre-impregnation stretch the gel filaments are ordinarilypassed directly to the relaxing impregnation bath. As indicated, theimpregnation bath is advantageously an aqueos bath maintained at between90 and about 110 C. Pressure may be applied to attain the highertemperatures or other solvents inert to the acrylonitrile polymer may'be added to raise the 'boiling point or aid in dissolution of the dyeassistant, or the dye assistant itself may elevate the boiling point ofthe solution. Beneficially, temperatures near the boil of the solutionare employed. While the gel filaments are in the impregnation bath theyare completely relaxed, that is, they are maintained at zero tension.The degree of relax will depend somewhat on the composition of the geland the dye assistant, and the time it is desired to keep the gelfilament in the impregnating solution. The relax can be expressed interms of stretch ratios and, beneficially, a stretch of between about0.2 and 0.9 times is used. This means that the gel filaments are removedfrom the impregnating bath at 0.2 to 0.9 times as fast as they enter.

Following the impregnation of the filaments with the dye assistant theyare generally passed directly to the postimpregnation stretch and theregiven an ultimate stretch.

4 This stretch influences the impregnation, but is principally directedto impart the final orientation to the filament molecules to the pointwhere they will have acceptable physical properties. This will bedetermined in large part on the amount of stretch given in thepre-impregnation step. Ordinarily, this stretch will range from greaterthan one up to 6 to 8 times so that the filament will have a totalstretch from about 8 to 20 times its washed length. As with thepre-im-pregnation stretch, the post-impregnation stretch is carried outin an aqueous medium which i may be steam but is preferably a water bathmaintained at to C.

The invention is applicable to treating acrylonitrile polymer fiberswhich are fabricated from fiber forming acrylonitrile polymers thatcontain in the polymer molecule at least about 80 weight percent ofpolymerized acrylonitrile, and is especially applicable to the treatingof homopolymeric acrylonitrile, which are wet spun in and 'with systems,that are adapted to utilize aqueous coagulating liquids in the spinningoperation, such as systems wherein ethylene glycol, dimethylformamide,di-

methylsulfoxide, butyrolactone and the like or the various salinepolyacrylonitrile-dissolving solvents are employed as spinning solutionsolvents for the polymer and are also present in non-polymer dissolvingquantities in the aqueous coagulating liquid used in the spin bath.

The utile, known aqueous saline solvents for the various fiber formingacrylonitrile polymers and polyacrylonitrile include zinc chloride, thevarious thiocyanurates such as calcium and sodium thiocyanate, lithiumbromide, salt mixtures of the so-called lyotropic series, and othersrecognized by the art as has been disclosed, among other places, inUnited States Letters Patent Nos. 2,140,921; 2,245,192; 2,648,592;2,648,593; 2,648,646; 2,648,648; 2,648,649; and 2,949,435.Advantageously, aqueous zinc choride solutions are used for the purpose.

Exemplary of some of the monomeric material that may. be employed withthe acrylonitrile in the preparation of the acrylonitrile polymer. andcopolymer fiber forming systems and treated in accordance with thepractice of the present invention include allyl alcohol, vinyl acetate,acrylamide, methacrylamide, methyl acrylate, vinyl pyridine, ethylenesulfonic acid and its alkali metal salts, vinyl benzene sulfonic acidand its salts, 2-sulfoethylmethacrylate and its salts, vinyl lactamssuch as vinyl caprolactam and vinyl pyrrolidone, etc. and mixturesthereof.

As indicated, after acrylonitrile polymer fibers have.

been wet spun they are most frequently Water washed or washed with anaqueous inert solution to remove any. residual polymer solvent from thefreshly formed fila-, ments, thus forming an intermediate fiber productoften referred to as a gel or aquagel filament. Thoroughly washedacrylonitrile polymer aquagel fibers, incidentally, are usually found tocontain up to about 6 parts by weight of Water (including residualextrinsic or exterior water associated therewith) for each part byweight of dry polymer therein. More frequently, washed acrylonitrileaquagel polymer fibers are found to contain from about 3 to 4 parts byweight of water for each part by weight of polymer.

The present invention can be carried out conveniently in standardspinning trains. That is, no major alterations to a conventional fiberforming process need be undertaken except to provide the necessarystretch and dye assistant impregnation baths. Because of the extremespeed at which the fibers can be impregnated in practicing the presentinvention, the ordinary and commercially useful spinning speeds can beemployed while simultaneously obtaining an excellent dye receptivefiber.

Essentially any additive that will enhance the dyeability of theacrylonitrile polymer fiber can be incorporated in the gel in accordancewith the present invention. Beneficially, the dye assistant is watersoluble or at least water dispersible so that it can be applied from awater.

bath; however, other solvents or mixtures of solvents may be employedfor dissolving or dispersing the dye assistant. If the dye assistant isa liquid itself, it can be used at full strength, although more dilutesolutions are preferred. Any suitable temperature can be employed forthe impregnation, for example, from room temperature up to the boilingtemperature of the particular solution in use. When water is used,advantageously, the impregnation bath is maintained at about 90-l00 C.

The amount of the dye assistant that is applied to and impregnated inthe acrylonitr'ile polymer gel is usually about at least 1.0 weightpercent, based on dry fiber weight. Preferably, between about 2 and 15percent of the additive is impregnated in the fiber, based on dry fiberweight, but amounts up to 30-40 percent can be utilized in someinstances without deleterious efiects. The impregnation bath usuallycontains relatively dilute solutions of the dye assistant. For mostpurposes, between about 1 and weight percent of the assistant, based onsolution weight, is adequate to obtain the desired level of additive inthe fiber, but concentrations up to the saturation point of theassistant in the solvent can be used. Any conditions that tend to causeagglomeration of the dye assistant should be avoided for obviousreasons.

Exemplary of the types of dye assistants that can be impregnated in thegel fiber in accordance with the invention include:

(1) Water-soluble amine salts, including:

Octadecyl ammonium acetate Octadecyl ammonium chloride Di-n-amylammonium chloride Tri-n-amyl ammonium chlorideN-2-[2-(2,2,3,3-tetramethylbutyl phenoxy) ethoxy] ethyl- N,N-dimethylammonium chloride N-2-(octadecyloxy)ethyl-N-N-dimethyl ammonium chlorideN-Z-(decyloxy)ethyl-N,N-dimethyl ammonium chlorideN-Z-(heptoxy)ethyl-N,N-dimethyl ammonium chlorideN-oxtadecyl-N,N-di-(Z-hydroxyethyl) ammonium chlorideN-dodecyl-N,N-di-(Z-hydroxyethyl)ammonium chloride 2-n-nonyl pyridinehydrochloride 5-ethyl-2-n-nonyl pyridine hydrochlorideN-n-octadecylpiperidine hydrochloride 2-heptadecyl-3-(2-hydroxyethyl)glyoxalidine hydrochloride 2-heptadecyl-3-butyl glyoxalidinehydrochloride 2-heptadecyl glyoxalidine hydrochlorideDi-(carboxymethyl)dodecyl ammonium chloride (2) Quaternary ammoniumsalts, including:

n-Nonyltrimethyl ammonium bromide n-Decyltrimethyl ammonium bromiden-Dodecyltrimethyl ammonium chloride n-Hexadecyltrimethyl ammoniumchloride nOctadecyltrimethyl ammonium chloride n-Dodecylbenzyltrimethylammonium chloride n-Dodecyltolylmethyltrimethyl ammonium chloriden-Decyloxyethyltrimethyl ammonium iodide 11 [2(2,2,3,3-tetramethylbutylphenoxy)ethoxy] ethyltrimehtyl ammonium iodideCarboxymethyl dimethyl tetradecyl ammonium chlorideBenzylhexadecyldimethyl ammonium chloride Benzyl (2,2,3,3tetramethylbutylphenoxy) ethyldimethyl ammonium chloride2-hydroxyethyl-n-octadecyldimehtyl ammonium bromiden-Dodecyl-bis-(Z-hydroxyethyl) methyl ammonium bromideBis-(Z-hydroxyethyl)methyl-n-octadecyl ammonium bromideBenzyl-Z-[Z-(2,3,4,6-tetrachlorophenoxy)ethoxy] ethyl morpholinumchloride Ethyl-n-octadecyl morpholinium ethosulfate n-Dodecyl pyridiniumchloride n-Hexadecyl pyridinium chloride n-Dodecyl isoquinoliniumbromide Bis-(polyoxyethylene oleate) ethyl methyl ammonium ethosulfateTrimethylene bis(dimethyl-n-tetradecyl ammonium bromide) Trimethylenebis [n-dodecyl-di-(Z-hydroxyethyl) ammonium bromide] Trimethylene bis[2,2,3,3 tetramethylbutyl phenoxyethoxy) ethyl dimmethyl ammoniumchloride] Tetramethylene bis(n-dodecyldimethyl ammonium chloride)Pentamethylene bis(n-dodecyldimethyl ammonium chloride)Poly-4-methyltrimethyl ammonium stearyl chloride Dimethyl Z-hydroxyethylstearamidopropyl ammonium chloride (3) Water-soluble sulfonium salts,including:

n-Dodecyl dimethyl sulfonium chloride, bromide or methosulfate n-Dodecylethyl methyl sulfonium halide or alkylsulfate n-Dodecyl methyl octylsulfonium methosulfate n-Tetradecyl ethyl methyl sulfonium metho'sulfate2[2-(2-biphenyloxy)ethoxy]ethyl butyl methyl sulfonium methosulfateDi-n-dodecyl methyl sulfonium methosulfate Di-(Z-hydroxye-thyl)methylsulfonium methosulfate, clicapric ester Di-n dodecyl dimethyl ethylenedisulfonium' di-methosulfate n-Octadecyl dimethyl sulfoniumbromiden-Dodecyl benzyl methyl sulfonium methosulfate Cetyl p-tolyl methylsulfonium methosulfate n-Octadecyl Z-(diethyl methyl ammonium)ethylmethyl sulfonium dimethosulfate Cetyl dimethyl sulfonium methosulfaten-Dodecyl 2-chloroethyl methyl sulfonium 2-chloroethyl sulfate2[2-(4-cyclohexylphenoxy)ethoxy] ethyl diethyl sulfonium ethosulfate (4)Water-soluble phosphonium halides, including:

Triethyl n-octyl phosphonium iodide n-Dodecyl trimethyl phosphoniumbromide Cetyl trirnethyl phosphonium chloride Trimethyl n-octylphosphonium chloride Benzyl tri-n-butyl phosphonium chloride I Benzyln-dodecyl dimethyl phosphonium bromide Benzyl cetyl dimethyl phosphoniumiodide Dichlorobenzyl triphenyl phosphonium chloride (5 Water-solublepolymers of N-vinyl pyrrolidone and related compounds, including:

N-vinyl n-methyl formamide N-vinyl N-ethyl formamide N-vinyl N-methylacetamide N-vinyl N-ethyl acetamide N-vinyl valerolactam N-vinylcaprolactam N-vinyl morpholinone N-vinyl oxazolidinoneN-vinyl-S-methyl-oxazolidinone (6) Polymers of aromaticalkenyl-containing sulfonic acid compounds including:

Para-styrene sulfonic acid Sodium para-styrene sulfonate Methylpara-styrene sulfonate 2-chloro-4-vinyl benzene sulfonic acid (7)Polymers of alkenyl sulfonic acid compounds including:

Ethylene sulfonic acid Sodium ethylene sulfonate Methyl ethylenesulfonate l-butylene-3-sulfonic acid (8) Polymers of sulfoalkylacrylatecompounds in cluding:

Sulfomethylacrylate 2-sulfoethylacrylate In order to further illustratethe invention, a tow of polyacrylonitrile aquagel fiber, which fiberscontained from about 4 to 5 parts by weight of Water in the gel phase toeach part by weight of dry polymer in the aquagel 5 structure, wasobtained by extruding a spinning solution Lsulfoethylmethacrylate methylester comprised of about parts of polyacrylonitrile dissolved Polymers0f y y taulihe and homolog in about 90 parts of a 60 weight percentaqueous solution pounds including: of zinc chloride into an aqueouscoagulating bath that ac W1 01 taufine contained about 44 weight percentof zinc chloride dis- N-methwyloyl amine methyl ester i33 $55 51;a?Zd teiZdin a? Sill-Z1 53323; Methyl Nqnethacryloylammomethane sulfonatethrough a spinnerette having about 500 round, 3 mil diam- Pfeferahly,the Water Soluble of Water dispefsfhle P eter orifices. The coagulatedtow bundle after emerging mel'ie y assistants are p y in the Praetlee ofthe from the coagulating bath was washed substantially free invention.The polymeric assistants tend to have better f l by passing i throughsequential water b th resistance to Washing and other Processingtreatments, and at ambient temperature. It was then wet stretched in a awater solution is more conveniently handled and is less hot watertrough, some f hi h Contained a d i t t, hazardous and expensive thanconventional organic solto partially Orient h l fiber F ll i h i lVelltS- profitably, P y of y Pyrrohdone and orienting or stretching ofthe fibers, the aquagel tow bun- N-vinyl m0rph01in0n ar H dle was passedinto and impregnated with a dye assistant Depending n t ye assistant p yP solution consisting of an aqueous solution of poly-N- Hated can he ywith one of several of a Wide vinyl-Z-pyrrolidone, (PVP), maintained atabout 100 C. Variety of dyestuffs, among those that y mentioned The towbundle was either allowed to relax, or was are the V311, Sulfur, difeet,'metalliled, basic acid, aZOie, stretched while in the impregnatingsolution. acetate, reactive, ingrain and the like classes Of dyestuffs.The tow of aquagel' filaments was withdrawn from the AS mentioned, Whenthe acrylonitrile P y P impregnation bath and passed directly to thepost-impreglarly polyacrylonitrile, fibers are being manufa u Zinenation stretch bath where the filaments were stretched in chloride maymost advantageously be utilized as the sole, water at about 100 C.Subsequently, the fibers were or at least the principal saline solute inthe spinning sOlirreversibly dried in a hot air oven at about 140 C. forvent employed for the polymer. In such instances, the 7 9 minutes ttextile fibers, aqueous solution of zinc chloride in the spinningsolution The dried fibers were dyed with a 3% Irgalon Blue RL mayadvantageously be in a concentration range of from dye solution (basedon dry fiber weight), a 2:1 metal 55 to 65, preferably about 60 weightpercent, based on complex dyestuif after which random samples were se-.-the weight of the aqueous solution. The quantity of sublected from eachgroup of fibers of which cross-sections stantially pure water passedcountercurrent to the filawere examined under a microscope to determinethe. ments in the coagulation bath, should be sufiicient, whenpenetration of the dyestuff into the crosssection. The such aqueous zincchloride spinning solutions are emconditions used for the fiberpreparation and results obployed, so as to maintain the concentration ofzinc chlotained are set forth in the following table.

Pre-Impregnaiion Stretch (and Impregnation) Impregnation Bath PostImpregnation Stretch Sample '1" T st t h P t T s h (as ea;- (S 33 lit s.ee see an estate 7. 0 100. 0 16X None 1 10. 0 1. 5 1. 06X 17. 0X 75 13.3100.0 8X None 1 10.0 1.5 2.12X 170K 09 1.3 70.0 8X None 1 10.0 1.5 2.12X17.0X Ring 2 2. 4 70. 0 4X None 1 10. 0 1. 5 4. 25X 17. UK 25-50 24 674X 6. 0 7. 5 None 1. 04X 12. 5X Ring 24. 0 67 4X 6. 0 20. 0 4. 0 5. 2X12. 5X 75 24. 0 30 4X 6.0 20. 0 4. 0 4. 8X 12. 5X 50 1 Tow samples weretaken from pre-impregnation stretch and hand relaxed in impregnationbath, then hand stretched to 17X in post-impregnation stretch to obtainindependent times in the second pan.

2 Short times in preirnpregnation stretch were obtained by utilizingonly part of the trough.

ride in the portion of the liquid in the spinning zone at anon-polymer-dissolving coagulation concentration of at least about 25weight percent; advantageously from about 30 to 50 percent by weight andpreferably between about 40 and percent by weight. In such aqueous zincchloride systems for acrylonitrile polymers, wherein the freshly wetspun polymer is generally obtained in an aquagel form, it is generallydesirable for the spinning solution that is extruded to contain betweenabout 4 and 20 percent by weight of dissolved polymer; moreadvantageously from about 6 to 15 weight percent of dissolved polymer;and preferably particularly when polyacrylonitrile fibers are beingmanufactured, from about 8.1 to 11.5 percent by weight of fiber-formingpolymeric solids in the spinning solution.

Aqueous zinc chloride spinning solutions of fiber-forming acrylonitrilepolymers are beneficially extruded at a spinning temperature from 0 to0, preferably from about 10 to 30 G, into an aqueous zinc chloridecoagulating liquid that is maintained at a coagulating temperature of 0to 30 (1.; preferably from about 10 to 20 C.

Similar excellent results to the foregoing are obtained when otheracrylonitrile polymer and other of the dye assistants are employed inaccordance with the invention.

What is claimed is:

1. A method for improving through dyeability of acrylonitrile polymerfibers comprising (a) spinning a solution of a polymer of an ethyleni- 9(e) stretching said impregnated filaments in an aqueous medium at about901l0 C.; and, (f) subsequently, irreversibly drying said filaments totextile fibers. 2. The, method of claim 1, wherein said acrylonitrilepolymer is polyacrylonitrile.

3. The method of claim 1, wherein said solution is an aqueous zincchloride solution.

4. The method of claim 1, wherein said aqueous medium of (c) is water at95-100 C. V

5. The method of claim 1, wherein said filaments are partially.stretched in (c) between about 4 and 8 times their washed length.

6. The method of claim 1, wherein said liquid bath of (d) is an aqueousbath.

7. The method of claim 1, wherein said liquid bath References Cited bythe Examiner UNITED STATES PATENTS 2,899,262 8/1959 Stanton et al264-182 X 3,097,054 7/ 1963 Routson et al 264182 X 3,104,934 9/1963Blumenkopf 264182 X ALEXANDER H. BRODMERKEL, Primary Examiner.

B. SNYDER, Assistant Examiner.

1. A METHOD FOR IMPROVING THROUGH DYEABILITY OF ACRYLONITRILE OLYMERFIBERS COMPRISING (A) SPINNING A SOLUTION OF A POLYMER OF ANETHYLENICALLY UNSATURATED MONOMERIC MATERIAL CONTAINING AT LEAST ABOUT80 WEIGHT PERCENT OF POLYMERIZED ACRYLONITRILE INTO AN AQUEOUSCOAGULATING BATH TO FORM FILAMENTS OF SAID POLYMER; (B) WASHING SAIDFILAMENTS ESSENTIALLY FREE OF ANY RESIDUAL SPINNING SOLUTION SOLVENT;(C) PARTIALLY STRETCHING SAID WASHED FILAMENTS IN AN AQUEOUS MEDIUM ATABOUT 90-110*C.; (D) RELAXING SAID PARTIALLY STRETCHED FILAMENTS ATBETWEEN ABOUT 90* AND 110*C. IN A LIQUID BATH OF A DYE ASSISTANT AGENTCAPABLE OF ENHANCING THE DYEABILITY OF SAID FILAMENTS AND IMPREGNATINGSAID FILAMENTS THEREWITH; (E) STRETCHING SAID IMPREGNATED FILAMENTS INAN AQUEOUS MEDIUM AT ABOUT 90* AND 110*C.; AND, (F) SUBSEQUENTLY,IRREVERSIBLY DRYING SAID FILAMENTS TO TEXTILE FIBERS.